SemiSouth power Jfets .......... FW J2

[sp300b]

100 Ohm is not a must ....ZM advice is starting with 47Ohm and going up and let the ears decide......

ZM don't know

[Zen Mod]

ZM weiß Bahnhof:Viannen_loungelizard:

[sp300b]

Test Setup connected, Concept is Working and here comes the measurements done tonight.

Seems to be very stable, On osciloskope over 100 KHz there is no problem with Square input.

Additionall small tweeking of the elements seems to be required....

for ZM - I didn't changeR25 trimmer from the starting position.

edit : schm deleted by ZM

[Zen Mod]

Test Setup connected, Concept is Working .........

:buehehe:you have doubts ?

........Seems to be very stable, On osciloskope over 100 KHz there is no problem with Square input............

and even more , at least with my parts/outputs/gate resistorsI have some notes in my workshop , along with CRO screenshots , but they're completely boring - nothing to write home about .

........Additionall small tweeking of the elements seems to be required....for ZM - I didn't changeR25 trimmer from the starting position.

whatever it needs ; these Jfets are trickier to set , comparing to big ole mosfets , due to smaller Ugs .... and wild xconductance ; but - as I said before - nothing to worry aboutplain boring amp - to make

[sp300b]

I've just started playing with this toy....Myth will be 100 % Busted in a coming days

[Zen Mod]

I like that ........

sp300b & ZM ........ Mythbusters

and - one member on Big Diya

[sp300b]

I like that ........

sp300b & ZM ........ Mythbusters

and - one member on Big Diya

Yea, One really BIG FuLLrange man

[Zen Mod]

Yea, One really BIG FuLLrange man

http://www.diyaudio....-spavleski.html

"Spavleski" Slobodan Pavleski is an electronics engineer and his professional bio is even longer than this article! He is 42 years old, audio and music are his hobby and ZM sez: “One hell of an engineer!”

[sp300b]

Busted !

[sp300b]

Here comes Schematic Nomenclature according to my PCB

edit : schm deleted by ZM

[Zen Mod]

yup - nomenclature made by mistake of pcb maker:rofl:

[sp300b]

Here comes Schematic Nomenclature according to my PCB

And according to previous picture, here comes where to measure

[Zen Mod]

:connie_nutzo:taking in account that just 6 pairs are made ....... and that's probably all what will be made:cheers:

[sp300b]

:connie_nutzo:taking in account that just 6 pairs are made ....... and that's probably all what will be made:cheers:

Anyhow, Do you agree with a measurement points shown previously (where and how) ?

[Zen Mod]

yes , indeed .......... certainly ...... why not ........ how else ..........

[Magura]

Anyhow, Do you agree with a measurement points shown previously (where and how) ?

Now that I've spent a lot of time tuning the Donuts, one thing I learned was that next time I make a PCB, I will make pads for measuring points. You seem to have plenty of room for that (so did I, but did not think of it back then).Magura

[sp300b]

Now that I've spent a lot of time tuning the Donuts, one thing I learned was that next time I make a PCB, I will make pads for measuring points. You seem to have plenty of room for that (so did I, but did not think of it back then).Magura

[sp300b]

Some more thinking given as comments in red

edit : schm deleted by ZM

[Sipi]

Slobo, zaista je nesto manji napon na R69 - probaj da stavis manji R70 (recimo 1k), ili je Q26 malo van specifikacije (mada ne bi smelo tol'ko)...

[sp300b]

If You have Vgs measured as 1,32V at 2A, then expect Vgs+Rds to be around 2,4V, not 2,7V....

[sp300b]

Slobo, zaista je nesto manji napon na R69 - probaj da stavis manji R70 (recimo 1k), ili je Q26 malo van specifikacije (mada ne bi smelo tol'ko)...

Hvala sipi...Ja sam svuda umesto 12K stavio 15K...verovatno je tu zez....Mozda promenim sva3 komada na 10K.

[Sipi]

Stavi i manje (1k) jer taj otpor limitira struju kroz bazu Q27 i kolektor Q26 - sa tako visokom vrednoscu R70 kroz Q26 jedva teku neki tanki mikroamperi a posto ima visok beta faktor naravno da ce Vbe biti jako mali.